1. Field of the Invention
The invention relates generally to fuel systems and, more particularly, to systems and methods for monitoring operating conditions within an aircraft fuel pump for automated shutdown.
2. Description of the Related Art
An aircraft fuel system must provide for storage of the required amount of fuel and for the delivery of this fuel to the engine(s) at the proper rate and pressure. Nearly all aircraft engines, and particularly complex aircraft using high powered turbine engines, are equipped with a pressure fuel-feed system. In these systems, fuel is drawn from fuel tanks by electrically-driven primary fuel pumps and delivered to the engine at the desired pressure. Alternate fuel pumps serve as backups if a primary fuel pump fails, the alternate fuel pumps providing built-in redundancy in the fuel supply system. The fuel pumps are designed to deliver a continuous supply of fuel at the proper pressure at all times during engine operation. The absence of fuel at the proper pressure within the fuel pump may be indicative of an inadequate fuel supply to the pump. Such a condition is often referred to as a “dry-run” condition. Failure to detect a dry-run condition may cause irreparable pump damage, and could ultimately lead to pump failure and a possible fire danger.
In an attempt to avoid pump damage, complex aircraft which are equipped with fuel pumps are often provided with some type of fuel-pressure warning system. Known pressure warning systems generally include a pressure switch positioned within the fuel pump. When the fuel pressure drops below a safe minimum, the pressure sensor outputs a signal which in turn, illuminates a warning light situated in a conspicuous place in the instrument panel to serve as a warning to the pilot. The engine can continue to run because of built-in redundancy in the fuel supply system, usually provided by backup pumps. However, such, existing fuel systems employing known pressure warning mechanisms require operator input to avoid potentially dangerous pump operating conditions in response to warnings provided by the sensors.
In addition to inadequate fuel pressure within a fuel pump, a high temperature within a fuel pump may also be indicative of a dry-run condition. The presence of adequate fuel tends to keep the internal temperature of the fuel pump at or below a safe operating temperature. When inadequate fuel is present, the operation of the motor within the fuel pump causes the internal temperature to increase. When the fuel pump internal temperature is above the safe operating temperature for a prescribed time interval, a dry run condition may exist. The safe operating temperature and the prescribed time interval are dependent on the type of aircraft and pump. Conventional aircraft fuel pump systems do not take the temperature of the fuel pump into account when mounting pump operations.
Those skilled in the art have recognized a need for fuel systems that eliminate the need for operator intervention when certain operating conditions within the system fall outside of an acceptable range of operation. The need for a system capable of monitoring fuel pump temperature has also been recognized. The invention fulfills these and other needs.